The present invention relates to a truss structure for use in a roofing and the like of a building.
As a space truss structure which can shorten the term for completion of work by facilitating the connection of its chord members, a conventional truss structures is disclosed in JPA Laid-Open No. 60-89744. A connection member is provided on one surface of which a connection tube for connecting chord members is erected, and on the other surface of which a rib for connecting diagonal chord members is mounted, whereby chord members each having a connecting part on, the end thereof are connected thereto via washers which may be in any numbers. Further, JPA Laid-Open No. 5-311765 discloses a flat metal square column pipe member having a concave cross-section fitting member on both ends thereof formed by press or roll working, and wherein the concave cross-section fitting part is provided with a long narrow opening for fitting which is pierced therethrough. Still further, a double pipe type truss beam which integrates an upper chord member and a lower chord member formed of a pipe, and a web member is disclosed in JPA Laid-Open No. 7-180217. Still further, JPA Laid-Open No. 61-100704 discloses a connection structure for a truss joint which is comprised of joining diagonal pipe members via a cross gausset plate to an M-shaped, H-shaped chord members or to a vertical pipe member, wherein a backup member outside the truss plane of the gausset plate is omitted such that the bore of the pipe between a flange and a web of the chord member is effectively utilized.
As mentioned above, various efforts have been made in order to facilitate the connection of the chord members and shorten the term for completion of work. Also, it is known to flatten the connection edge of the chord member by compression pressing to this effect. In this conventional structure, however, existence of a free plastic deformation part, which is elliptic and extends between the flat surface provided by compression pressing and the complete round section of a parent pipe member cannot be avoided. This long and narrow free plastic deformation part adjoining the connection end structure flattened by compression according to the conventional method is not only unnecessary but also disadvantageous in the truss structure because the size of the parent plate for connecting the chord member using a bolt thereto becomes inevitably large. Provision of such a large sized parent plate has been a cause to increase the size of its joint structure, thereby decreasing its rigidity, and increasing the cost of manufacture.
An object of the present invention is to provide for a truss structure which can improve its rigidity by reducing the size of its joint structure, and lower the cost of manufacture by reducing the size of its parent member plate.
Another object of the invention is to provide for structural members suitable for use in constructing this truss structure, and a method of manufacture thereof.
One of the features of the present invention resides in an edge portion of a pipe being forcibly pressed between an upper die and a lower die, each having a same cylindrical surface of constraint. By use of such dies, it becomes possible to directly form a flat surface section on the edge of a pipe member while securing a complete round portion thereof serving as a parent member. Therefore, the long free plastic deformation part which is inevitably formed using the conventional dies having a flat surface portion for forming a conventional flat structure can be eliminated, and a connection edge having a flat surface which is directly connected to the complete round parent member can be realized according to the invention. The present invention, as stated above, is characterized by the forced constrained pattern pressing of the edge portion of the pipe using the upper and the lower dies having a cylindrical semi-surface of constraint. However, it is not limited thereto, and a modification of which for providing a polygonal or a short elliptical structures instead of the cylindrical is within the scope of the invention. Essentially, in forming the flat section, it is intended to form a constrained tubular portion between the flat section and the complete round parent member by a constrained pattern forming press, and the shape of this constrained tubular portion may be the same as the pipe as the complete round parent material or any shape required in its design.
More specifically, the truss structure, structural members therefor and the method of manufacture thereof as will be described below are provided according to the invention.
The present invention provides for the truss structure for connecting an upper chord member, lower chord member and diagonal chord member to its parent plate via respective connection parts of each member provided on both ends thereof, wherein the upper chord member, the lower chord member and the diagonal chord member used is a pipe member, and wherein the connection part of the pipe member is comprised of a tubular portion forcibly shaped into the same diameter and the flat surface portion formed integral with the tubular portion by compression pressing, further wherein the connection part is connected to the parent plate via a bolt opening provided in the flat surface portion.
Preferably, the connection part member includes the parent plate and a rib member erected cross-wise thereon, and each edge portion of each flat surface part is tapered and arranged in juxtaposition.
The truss structure according to the invention has the upper chord member, the lower chord member and the diagonal chord member, each having the connection part on the both ends thereof for connecting to the parent plate therethrough. The upper, the lower and the diagonal chord members use a pipe member, and the connection part has a flat surface portion formed by the compression pressing, with the edge portion of the flat surface portion being tapered. Assuming a distance (2xc3x971) between connection center positions of two flat portions of juxtaposed two chord members to be U1xe2x80x3 when divided by 2, and a diameter of a bolt opening provided in the flat surface portion to be xe2x80x9cdxe2x80x9d, the following relationship between xe2x80x9c1xe2x80x9d and xe2x80x9cdxe2x80x9d exists.
xe2x80x831xe2x89xa6{square root over (2)}t/2+10{square root over (2)}+2.0d+B/2, and 1 greater than 3d (in mm).
According to one aspect of the invention, the truss structural members include the upper chord, the lower chord and the diagonal chord members, each having a connection part on the both ends thereof. The connection part is comprised of the tubular portion forcibly formed into the constrained pattern with a constrained restriction, and the flat surface portion formed integral with the tubular portion by flat pressing, and the bolt opening is provided in the flat surface portion.
According to another aspect of the invention, the die is provided for forming the connection part on the edge portion of the truss structural members such as the upper chord, the lower chord and the diagonal chord members, which are tubular, wherein the die is comprised of an upper press die and a lower press die. Each die has a half tubular curved surface open to the outside and placed oppositely to provide for a constraint groove in combination whereby a constrained pattern is able to be formed.
According to still another aspect of the invention, the method for manufacturing the truss structural members such as the upper, the lower and the diagonal chord members which are provided with respective connection parts on both ends thereof comprises the steps of: placing a pipe between the upper and the lower press dies, each having the half tubular curved surface which is open to the external and positioned oppositely so as to provide for in combination one constrained shape; and simultaneously forming the flat surface portion connected integral with the tubular portion by pressing.